Remarkable electron-withdrawing effect of the Ph₂P(O)-ethynyl group: Ph₂P(O)-ethynyl-substituted aryl halides and copper acetylides for tailor-made Sonogashira couplings

Abstract

Ph2P(O)-ethynylphenyl bromide showed higher reactivity in Sonogashira couplings than phenylethynylphenyl bromide because of the electron-withdrawing nature of the Ph2P(O) group.

New Ethynylphenylborasilsesquioxanes—Their Reactivity and Behavior during Thermal Decomposition

“…In the first stage of catalytic tests, the reactivity of A with simple compounds containing the Si–H bond—triethyl and triethoxysilane—was investigated ( Table 1 ). Compared to the vinyl equivalent of silsesquioxane, the reaction with trimethylsilane occurs, and this may be due to the higher polarity of the ethynyl group and the strong electron-withdrawing effect [ 44 ]. In the case of a reaction with triethoxysilane, a complex reaction mixture is also formed and a back-biting reaction takes place, i.e., a redistribution reaction involving the transfer of an alkoxy group from silane to boron, occurring between siloxyboranes and alkoxysilanes [ 38 ].…”

Dephosphinylative [4 + 2] Benzannulation of Phosphinyl Ynamines: Application to the Modular Synthesis of Polycyclic Aromatic Amines

“…In contrast, the electronically balanced 4′-Me-substituted 2-bromobiphenyl 2d gave the corresponding product 4e in 80% yield (entry 4), whereas the electron-deficient 4′-CF 3 - 4f and 4′-NO 2 - substituted derivatives 4g were isolated in somewhat low yields (68% and 33%), respectively (entries 5 and 6). Thus, the highest yields were achieved with the electronically balanced derivatives 2a (78%) and 2d (80%) because in electron-sufficient aryl halides, Sonogashira–Hagihara coupling proceeded sluggishly but Friedel–Crafts cyclization did smoothly, and in electron-deficient aryl halides, vice versa.…”

One-Pot Transformation of Me3Si-/Ph2P(O)-Protected Ethynes to Unsymmetrical Arylethynes

“…8 Although trialkylsilyl groups such as trimethylsilyl (TMS) and t-butyldimethylsilyl (TBDMS) and the 2-hydroxy-2-propyl group are routinely used as protecting groups for terminal ethynes, the phosphoryl group (Ph 2 P(O)) has been developed as a new protecting group. [9][10][11][12][13] The high polarity of the phosphoryl group enables the easy separation of the desired products from the less-polar hydrocarbon by-products. 10,12 Recently, a short one-pot synthesis of unsymmetrical arylethynes has been developed involving dephosphorylation followed by Sonogashira couplings.…”

“…[9][10][11][12][13] The high polarity of the phosphoryl group enables the easy separation of the desired products from the less-polar hydrocarbon by-products. 10,12 Recently, a short one-pot synthesis of unsymmetrical arylethynes has been developed involving dephosphorylation followed by Sonogashira couplings. However, the isolation of products was tedious because of the similar R f values of the products and by-products, and the yields of products required improvement.…”